Fusion Pro-Series, steel Mainspring Housing, for Full Size Government size 1911 frames. CNC Machined from Carbon Steel bar-Stock, With Chain-Link back, Black finished. Will fit most all 1911 full size 5 inch Government pistols and Commander size pistols and Clones. All CNC machined in the USA,. No MiM, No Cast, ALL Solid CNC Machined Bar-Stock. Mfg: Fusion Firearms